Electrical condenser



Aug. 13, 1929. NHLLER 1,724,499

ELECTRICAL CONDENSER Filed June 1925 awn Mia" smut Patented Aug. 13, 1929.

PATENT OFFICE.

JOHN M. MILLER, OF WASHINGTON, DISTRICT OF COLUMBIA.

ELECTRICAL CONDENSER.

Application filed June 3,

My invention relates broadly to electrical condensers and more particularly to the plate construction for variable air condenser-s. Y

An object of the invention is to provide a movable plate for an electrical condenser having an are which subtends an angle of more than 180 degrees at the center of rota tion.

Another object of theinvention is to obtain a more uniform precision of setting in capacity at all angular settings of a condenser, including those near the setting for minimum capacity.

With the above and other objects in view the invention consists in. the construction, combination and arrangement of parts as will be hereinafter fully described.

In the usual type of semi-circular plate variable air condenser, the capacity of the condenser varies nearly linearly with the setting. When such a condenser is employed in a radio receiver or wave-meter circuit, the change in frequency of resonance of the circuit per division of the condenser setting is very small at high capacity settings relative to the change per division at low settings. In general, the scale of frequencies will be too crowded at the lower end or too open at the upper end for many purposes. To overcome this difficulty and also for other special purposes, condenser plates differing in shape from the semi-circular have been proposed. Such condenser plates depart from the semi-circular form in that the are r of the useful area of the plate subtends an angle of less than 180 degrees at the center of rotation.

In general it has been the practice to strive for a, low capacity in condensers at the setting for minimum capacity. I depart from this practice and obtainthereby a new and useful result'in that I obtain a more uniform precision of setting in capacity or frequency at all settings including those near the set ting for minimum capacity.

My invention will best be understood from the aoc dmpanying drawing in which is shown a condenser plate embodying the useful features of this invention.

In the figure, plate 1, drawn in solid line and assumed to represent the movable plate, has a useful area, the arc of which subtends an angle of nearly 360 degrees at the center of-rotation. The fixed plate 2, drawn in dash line, is the ordinary semicircular type.

1925. Serial No. 84,635.

As represented in the figure the movable plate has been revolved through a small angle in the direction of the arrow from the position of minimum capacity. It will be evident that the change in capacity for a certain small angle of further rotation from this posit-ion will be very small, because, while useful area is being added on the left, useful area is being subtracted on the right, the net setting is obtainable at all points of the scale.

By suitable choice of shape it is possible to obtain the condition that the per cent in capacity increase per unit of angular rotation is uniform'throughout the total range or that, in a frequency meter or receiver for heterodyne reception, the change in frequency,per unit of angular rotation is uniform throughout the range of the condenser.

It is obvious that similar results may be by interchanging the fixed and movable plates in the above described construction without departing from the spirit of the invention.

What I claim as new is:

1. In a. condenser the combination of a set of metallic rotor plates and a set of metallic stator plates, each rotor plate consisting of a plurality ofsemicircular segments integral with each other and lying 1n the same plane, the center of the diameter of one of the semicircular segments forming the center'of rotation of the rotor plate, the center of the diameter of the other segment positioned upon the diameter of the first segmenta distance removed from the center of the first segment, each stator plate having a straight edge but for a recess to accommodate the rotational. element of. the rotor plates, said straight edge being positioned so that it would intercept the axis of rotation of the rotor plates but for the recess and extending to substantially equal extent upon both sides of the center of rotation of said rotor plates to form a condenser, the rotor and stator plates of which are in active capacity relationshi throughout 360 degrees of rotation of said rotor plates.

2. In a condenser the combination of a set of metallic rotor plates and a set of metallic stator plates, each rotor plate consisting of a plurality of semicircular segments integral with each other and lying in the same plane, the diameters of the semicircular segments forming the juncture between the two segments, the center of the diameter of the first segment forming the center of rotation of the plate and the center of the diameter of the second se ment disposed along the diameter of the first segment at a distance removed from the center of rotation of the plate, each stator plate having a straight edge but for a recess to accommodate the rotational element of the rotor plates, said straight edge being positioned so that it would intercept the axis of rotation of the rotor plates but for the recess and extending to substantially equal extent upon both sides of the center of rotation of said rotor plates to form a condenser, the rotor and stator.

plates of which are in active capacity rela- -tionship throu hout 360 degrees of rotation of said rotor p ates.

3. In a condenser the combination of a set of metallic rotor plates and a set of metallic stator plates, each rotor plate consisting of a )lurality of semicircular segments integral with each other and lying in the same plane, the diameters of the segments parallel, the

' center of the diameter of one segment forming the center of rotation of the plate and the center of the diameter of the other segment removed from the center of rotation of the plate, each stator plate having a straight edge but for a recess to accommodate the rotational element of the rotor plates, said straight edge being positioned so that it would intercept the axis of rotation of the rotor plates but for the recess and extending to substantially equal extent upon both sides of the center of rotation of said rotor plates to form a .condenser, the rotor and stator plates of which are in active capacity relationship throughout 360 degrees of rotation of said rotor plates.

4. In a condenser the combination of a set of metallic rotor plates and a set of metallic stator plates, each rotor plate consisting of a plurality of semicircular segments of different size integral with each other and lying in the same plane, the diameters of the segments lying parallel, the center of the diameter of the largest segment forming the center of rotation of the plate, and the center of the diameter of the smaller segment removed from the center of rotation of the plate, each stator plate having a straight edge but for a recess to accommodate the rotational element of the rotor plates, said straight edge being positioned so that it would intercept the axis of rotation of the rotor plates but for the recess and extending to substantially equal extent upon both sides of the center of rotation of said rotor plates to form a condenser, the rotor and stator plates of which are in active capacity relationshi throughout 360 degrees ofrotation of said rotor plates.

JOHN M. MILLER. 

